CA1220598A

CA1220598A - Curable fluoropolymer composition

Info

Publication number: CA1220598A
Application number: CA000452673A
Authority: CA
Inventors: Walter W. Schmiegel
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1983-04-26
Filing date: 1984-04-24
Publication date: 1987-04-14
Also published as: EP0127318B1; DE3462910D1; JPS59206451A; EP0127318A1; US4489196A; BR8401886A

Abstract

TITLE
ABSTRACT OF THE INVENTION
A curable fluoropolymer composition containing a copolymer of vinylidene fluoride and hexafluoropropylene or the like, a vulcanization accelerator which is a quarternary ammonium compound or a quarternary phosphonium compound, a crosslinking agent such as a bisphenol, a divalent metal oxide or divalent metal hydroxide acid acceptor, and as a coaccelerator a polyol e.g. pentaerythritol or the like.

Description

5~

TI q'LE:
CUR~BLE F~UOROPOLYMER COMPOSITION
This invention relates to a fluoropolymer composition that may be cured to form fluoroelastomeric articles, and to the process of curing said composition to form such articles.
BACKGR~'~ND
It is known in the art to produce ¦ fluoroelastomeric articles by curing fluoropolymer compositions. U.S. Patent 3,876,654 to Pattison discloses such co~positions, processes for producing such articles, and such ar~icles.
The present invention is an improvement over the composition and process taught in the Pattison patent. I~ has now been ~ound that a faster cure can be obtained by use of the composition of the invention, or if desired the co~position can be cured at about the same rate as that taught in Pattison, bu. the resulting product will have improved compression set and reduced water swell.
The curable fluoropolymer composition taught by Patti~on contains:
l. A copolymer of viny~idene fluoride and ~ at least one other fluorinated monomer, ~Example o~
~ 25 such other monome~s include hexafluoropropylene, and mixtures o~ hexa~luoropropylene a~d tetra~luoroethylene]l

2. A quaternary phosphonium compouncl which acts as a vulcanization acceleratorj

3. A divalent metal cxide or hyd~coxide or mixtures of sai~ oxides or hydroxides with salts of weak acids, ~nd

4. A crosslinking agent.
It has now been found thzt the Pattison AD~5359 35 composition is improved by the addition of 3.2 to 4 . . . .

., ' ~
:: , 55~39 parts by weight, based on 100 part~ o~ the fluoropolymer of a polyol ~elected from the cla5s consisting of pentaerythritol, dipentaerythritol, trimethylol propane, and

5 2,2-dimethyl-1,3 propanediol. The polyol acts to accelerate the rate of cure, or if desired the polyol may replace a portion of the quaternary phosphonium compound accelerator and in doing so yields a composition that cures at about the same rate but results in a cured product having improved resistance to compression set. Finally the use of the polyol allows for the use of less metal oxide or hydroxide, and such a composition when cured has improved resistancs to steam or boiling water -- that is, it does not swell as much as the composition containing more divalent metal oxide or hydroxide.
- SUM~RY
The present invention is a composition that may be cured to form a fluoroelastomer. The composition comprises the following components: ~A) a copolymer containing polymerized vinylidene ~luoride units, and polymerized hexafluoropropylene units or instead of hexafluoropropylene, or l-hydro or 2-hydropentafluoropropylene units. The copolymer may contain other polymerized fluorinat~d monomer units, ~uch as tetrafluoroethylene units, chlorotrifluoroethylene units, bromotetrafluorobutene units, and the like. Processes for the preparation of such polymers are disclosed for ex~mple in the Pattison patent, U.S. Patent 3,876,~54 and in the Apo-theker et al. U.S. Patent 4,214,069. (B) A
quaternary phosphonium vulcanization accelerator or a quaternary ammonium vulcanization accelerator. Such phosphonium compounds havs the fcrmula:

0~8 _ _ +
R2 X ( )n R -- P - R

_ _ n wherein P is phosphorous; Rl, R2, R3, and R4 are selected individually from the g~oup: Cl-C20 alkyl, aryl, aralkyl, alkenyl, and the chlorine, fluorine, bromine, cyano, -OR, and -COOR substi~uted analogs thereof, R being ~elected from the group:
C1C20 alkyl, aryl, aralkyl, and alkenyl; and X
is selected from the groupO halide, sulfate, sulfite, ; ~arbonate, pentachlorothiophenolate, ;!~ 15 tetra1uoroborate, hexafluorosilicate, hexafluorophosphate~ dimethyl phosphate, and Cl-C20 alkyl-, aryl-, aralkyl-, and alkenyl-/-carboxylate and dicarboxylate: n is 1 or 2 and equal to the valence of the anion X, and are described and disclosed for this use in the Pattison pa~ent. In the above formula X can also be OAr or OArOH, where Ar is an aryl radical.
Such ammonlum compounds include ~hose ; disclosed in Kometani et al. U~S. Patent 3,86~,298 and Patel et al. U.S. Patent 3,655,727 as w~ll as cyclic amidinium salts of the formula 30 L ~J ~
(C) A polyhydrc>xy aromatic crosslinking agent such as: di-, tri-, and tetrahydroxybensenes, naphthalenes, and anthracenes, and bisphenols of the formula n(HO~ (o~)n ~( A) x~

wherein A is a difunctional radical such as an alip~atic, cycloaliphatic, or aromatic radical o 1-13 carbon atoms, or a thio, oxy, carbonyl/
sulfinyl, or sulfonyl radical; ~ is optionally substituted with at least one chlorine or fluorine atom, x is O or 1, n is 1 or 2; and any aromatic ring of the polyhydroxylic compound is optionally substituted with at least one atom of chlorine, fluorine, or bromine, a -C~o group, or a carboxyl or acyl radical (e.g., a -COR where R is OH or a Cl-Cg alkyl, aryl, or cycloalkyl grou~). It will be understood from the above bisphenol formula that the -OH groups can be attached in any position (other than number one) in either ringO Blends of two or more ~uch compounds can also be used. Such cro~slinking agents and tneir use in cuxing fluoropolymers is disclosed in the Pattison patent.
(D) A polyol coaccelerator selected from pentaerythritol, 2,2,-dimethyl-1,3-propanediol, trimethylol propane, and dipentaerythritol.
Pentaerythritol has the formula:
OH
, 2 HO C~2 C 2 OH
and in its pure form has a melting point of about 260.5C, but is sold commercially in an impure form (for example by Hercules as PE-~OO) having a melting 30 point of about 190 to 200C. The impure ~orm contains some dimer and higher aggregates, formed by the condensation of two or more molecules with formation of water. Either the pure pentaerythritol or the commercial form m~y be employed in this invention, and ~E~ a metal compound selected from the ~Z2Q~

3 group consisting of divalent metal oxide and divalent metal hydroxide and mixtureq of such oxides and hydroxides with metaL salts of weaX acids. The composition of the invention contains per 1~0 parts by weight of the copolymer, about 0.~ to 2.0 parts (preferably 0.3 to 1.5 parts) by weight of component (B) about 0.5 to 4 parts (preferably 1 to 3 parts) by weigh~ of component (C), about 0.05 to 4 parts (preferably 0.1 to 2.0 parts) by weight of component ~, 10 (D) and about 0.5 to 30 parts (preferably about 1 to

6 parts calcium hydroxide and 1 to 9 parts magnesium oxide) by weight of component (E). Optionally the composition may also contain up to about 50 part~
(preferably 15 to 35 parts) by weight of carbon black.
, 15 DETAIL~D ~SC~IPTION
Among the most useful component A copolymers are: copolymers of vinylidene fluoride and hexafluoropropylene, chlorotrifluoroethylene, l-hydropentafluoropropylene, or 2-hydropenta1uoropropylene and copolymers of I vinylidene fluoride, tetrafluoroethylene and i hexafluoropropylene or l-hydro or 2-hydropentafluoropropylene. "Copolymer" herein means the product of copolymerizing two or more monomers. Especially preferred are vinylidene fluori~e/hexafluoropropylene copolymers in which the monomer~ are combined in a molar ratio of about 85:15 to 50:50. Component ~ can also ~e any other vinylidene fluoride copolymer fluo-oelastomer which can be cured to useful products, for example copolymers of vinylidene fluoride and - hexa~luoropropylene or pentafluoropropylene with dichlorodifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene, bromotetrafluorobutene, ,35 ~Polymers of this type are shown in ~pothe~er et al.
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Paten~ 4,214,060), with fluorinated vinyl esters, with derivatives o~ perfluoroacrylic acid, and with fluorinated alkyl vinyl ethers; the latter can be illustrated by copolymers o~ vinylidene fluoride, hexafluoroethylene and a perfluoroalkyl perfluorovinyl ether.
Useful copolymers of ~inylidene fluoride and 1,2,3,3,3-pentafluoropropylene are described in U.S.
Patent No. 3,331,8~3, and copolymers of these two components with tetra~luoroethylene are described in U.5~ Patent No~ 3,335,106. The "other fluorinated monomer" of component A is preferably an ethylenically unsaturated monomer containing at least as many fluorine atoms as carbon atoms.
~- 15 An essenti~l ingredient of the composition ; is the component B accelerator.
Particularly preferred accelerators are benzyl triphenyl phosphonium chloride, -bromide, and -phenolates of aromatic dihydroxy compounds listed under component C, used either alone or blended with about 1-50 percent of another component ~ compound within the description set forth above, based on the total weight of accelerator. Other use~ul component B accelerators are illustrated as follows: methyl trioctyl phosphonium tetrafluoroborate, tetraphenyl phosphonium bromide ~nd -chloride, benzyl trioctyl phosphonium bromide and -chloride, methyl trioctyl phosphonium acetate, methyl trioctyl phosphonium dimethyl phosphate, methyl trioctyl phosphonium chloride, methoxyethyoxyethyl trioctyl phosphonium chloride, tetraoctyl phosphonium bromide, butyl trioctyl phosphonium bromide, l-carbethoxyethyl triphenyl phosphonium chloride, tetrabutyl phosphonium chloride, 2,4-dichlorobenzyl triphanyl phosphonium chloride, m-trifluoromethylbenzyl ~2~

trioctyl phosphonium chloride, 2,2,3,3-tetra1uoropropyl trioctyl phosphonium chloride, 2,2,3,3,4,4,5,5-octa~luoropentyl trioctyl phosphonium chloride, isobutyl triphenyl phosphonium bromide, 2-pcntyl triphenyl phosphonium bromide, 4-methylbenzyl triphenyl phosphonium chloride, 1 4-chlorobenzyl triphenyl phosphonium chloride, diphenylmethyl triphenyl phosphonium chloride, I m-trifluoromethylbenzyl triphenyl phospho~ium ¦ 10 chloride, 1-naphthylmethyl triphenyl phosphonium i chloride, 2-cyanobenzyl triphenyl phosphonium i bromide, 4-cyanobutyl triphenyl phosphonium bromide, ¦ a-carbe~hoxybenzyl triphenyl phosphonium bromide, carbethoxymethyl triphenyl phosphonium bromide, methoxymethyl triphenyl phosphonium chloride, allyloxymethyl triphenyl phosphonium chloride, allyl triphenyl phosphonium chloride, and tetrabutyl - phosphonium bromide.
Component C of the curable composition can be selected from known polyhydroxylic aromatic compounds capable o functioning as a cross-linking agent for the elastomeric copolym~r. For e~ample, the component C cross-linking agent can be any one of ~he following: di-, tri-, and tetrahydroxybenzenes, naphthalenes, and anthracenes, and bisphe~ols o~ the formula n(H\) ~H)n ~(~)x~
wherein A is a difunctional radical such as an aliphatic, cycloaliphatic, or aromatic radical of 1-13 carbon atoms, or a thio, oxy, carbonyl, sul~inylr or sulfonyl radical, A i 9 optionally substituted with a~ least one chlorin~ or fluorine atom; x is 0 or 1; n is 1 or 2; and any aromatic ring ¦ of the polyhydroxylic compound is optionally substituted with at least one atom o~ chlorine, ¦ fluorine, or bromine, a -CHO group, or a carboxyl or ', acyl radical (e~g., a -COR where R is OH or a Cl-C8 alkyl, aryl, or cycloalkyl group). It will , be understood from the ahove bisphenol ~ormula that ¦ the -OH groups can be attached in any position (other than number one) ? n either ring. Blends of ~wo or ~ more such co~pounds can also be used.
! lo Referring to the bisphenol formula shown in the previous paragraph, when A is alkylene, it can be for example methylene, ethylene, chloroethylene, fluoroethylene, difluoroethylene, 1,3-propylene, ; 1,2-propylene, tetramethylene, chlorotetramethylene, '! 15 fluorotetramethylene, trifluorotetramethylene, 2-methyl-1,3-propylene, 2-methyl-1,2-propylene, pentamethylene, pentachloropentamethylene, pentafluoropentamethylene, and hexamethylene. When A
i5 alkylidene, it can be for example ethylidene, dichloroethylidene, difluoroethylidene, propylidene, isopropylidene, trifluoroisopropylidene hexafluoroisopropylidene, butylidene, heptachlorobutylidene, hepta1uorobutylidene, pentylidene, hexylidsne, and l,l~cyclohexylidene.
When A is a cycloalhylene radical, it can be ~or exampl~ cyclohexylene, 2-chloro-1,4-cyclohexylene, 2-fluoro-1,4-cyclohexylene, 1,3-cyclohexylene, cyclopentylene, chlorocyclopentylene, fluorocyclopentylene, and cycloheptylene.
Furthermore, ~ can be an arylene radical such as m-phenylene, p-phenylene, 2-chloro-1,4~phenylene, 2-fl~oro-1,4-phenylene, o-phenylene, methylphenylene, dimethylphenylene, trimethylphenylene, tetr~Methylphenylene, 1,4-naphthylene, ~z~s~

3-fluoro-1,4-naphthylene, 5-chloro-1,4-naphthylene, 1,5-naphthylene, and 2,6-naphthylene.
One highly preferred component C
cross-linking agent is hexafluoroisopropylidene-bis(4-hydroxybenzene). A
second preferred cross-linking agent is 4,4'-dihydroxydiphenyl sulfone. A third preferred I cross-linking agent is 4,4'-dihydroxy-benzophenone.
Another very useful cross-linking agent is 2,4-dihydroxybenzophenone, especially when the preferred co~position described above is to be used j in applications requiring a rapid rate of cure plus good co~pression set properties at a relatively low cross-linking agent content, but not requiring ~he lowest po~,sible compression set values. Other useful component C cross-linking agents are illustrated by hydroquinone: by such dihydroxybenzenes as catechol, resorcinol, 2-methyl resorcinol, 5-methyl resorcinol, 2-methyl hydroqu1none, 2,5-dimethyl hydroquinone, and 2-t-butyl hydroquinone; and by such compounds as 1,5-dihydroxynaphthalene and 9,10-dihydroxyanthracene.
! The (D) component in the composition of the invention is a polyol, i.e. pentaerythritol, a known compound that is commercially available, or dipentaerythritol or 2,2-dimethyl-1,3-propanediol, or trimethylolpropane. The polyol acts as a coaccelerator in the vulcanization reaction.
The composition of the invention also contains component (E), a metal compound composed of a divalent metal oxide, such as magnesium oxide, zinc oxide/ calcium oxide, or lead oxide, or a ~ivalent metal hydroxide, or a mixture of the oxide and/or hydroxide with a metal salt or a weak acid, for example a mixture containing about 1-70 percent by weight of the metal salt. Among the useful metal l ~ S~B

¦ salts of weak acids are barium-, ~odium-, potassium-, ¦ lead-, and calcium-/-stearate, -benzoate, -carbonate, ¦ -oxalate, and -phosp~ite. The amount of the metal compound added generally i5 about 0.5-15 parts by I S weight per 100 parts of fluoroelastomer, about 2-10 ¦ parts being preferred. The metal compound I concentration to some extent affects the rate of cure, and below the preferred range the cure rate may sometimes be unduly decreased. Above the preferred range, the elastic properties o a cured fluoroelastomer are gradually impaired and it is, therefore, advantageous not to use too large amounts of the metal compound.
The metal compound serves a dual purpose.
It ab50rbs certain gaseous and aci~ic materials which are evolved during vulcani~ation and can chemically attack and weaken the fluoroelastomer. It also provides a long term aging stability. ~then using a ! metal oxide, it can be ~ompounded with a ~0 fluoroelas~omer stock either free or as a metal oxide - complex or chelate with organic complexing agents and ligands, such as c~clic polyethers, amines, phosphines, ketones, alcohols, phenols, or carboxylic acids.
The initial cure o~ the curable composition is pre~erably carried out by heating the composition in a con~ining zone for about 30 seconds to 30 minutes at a~out 149 to 220~. Conventional rubber curing presses, molds, extruders and the like provided with suitable heating and curing means can be used.
By using the present composition and process, on~ can overcome problems regarding the loss o~ resistance to high temperature compression set when high levels of phosphonium or ammonlum salt z~s~

accelerators are used, the limitation o~ maximum cure rate when fixed levels of phosphonium or ammonium salt accelerator are used and with fixed levels o~
inorganic bases such as Ca (OH)2 and MgO in the presencP o~ fixed levels of aromatic di- or polyhydroxy compounds such as 4,4'-hexafluoroisopropylidene diphenol (Bisphenol AF) or hydroquinone, or the limitation of resistance to swelling by boiling water of a fast curing and highly compr~ssion set-resistant vulcanizate. The use of polyol permits the use of shorter and more economical press ~uring cycles than could be attaine~ in its absence and affords vulcanizates that possess excellent physical properties.
; 15 EXAMPLE 1 A fluoroelastomer composition of the present invention is prepared, cured, and tested. The composition is prepared by blending the following on a 2-roll rubber mill whose rolls are at about 25C:
100 parts fluoroelastomer, 15 parts carbon black, 6 parts calcium hydroxide, 3 parts magnesiu~ oxide, 0.90 parts benzyltriphenylphosphonium chloride, 2.0 parts 4,4'-hexa~luoroisopropylidene diphenol (Bisphenol AF) and 2~0 parts ~ercules~ PE-200 (a mixture that contains about 88% pentaerythritol anA
about 12% poly-pentaerythritols, including dipentaerythritol). The fluoroelastomer is a vinylidene f}uoride/hexafluoropropylene/-tetrafluoroethylene 45:30:25 terpolymer whose Mooney Viscosity (~-10 at 121~C) is 75.
- Test results are shown in Table 1. Samples of the freshly prepared uncured compositions are used for measuring (a) curing characteristics with the oscillating disc cure meter according to ASTM Method D-2084 and (b) Mooney Scorch according to ~STM Method ~z~sg8 ¦ D-1646-63. Under "curing characteris~ics" the table I shows the time in minutes to reach 50% of full cure (t '50) and to reach a 0.2 N-m rise above the minimum torque (~s 0.2).
In preparing the cured samples, the pellets and slabs are press cured for 15 minutes at 177C at I a total force of abut 4 MN per m2 of mold area.
The cured samples are postcured for 24 hours at 232C in a circulating air oven. ~fter postcuring ~ 10 the cuxed samples are subjected to heataging by I exposure to circulating air for 7 days at 275~C in an oven. The modulus, tensile strength and elongation values are obtained at room temperature by ASTM
Method D-412. Compression set values are obtained by ~ 15 AST.~ Method D-395-61.
`1 The fluoroelastomer composition of Example 1 j is very useful for the rapid manufacture of cured fluoroelastomer articles having excellent physical ~ properties (as indicated in Table l); relatively ¦ ~0 short and economical press-curing cycles can be used j to manufacture such articles. The Example 1 ¦ composition can be used for the manufacture of heat and solvent resistant and resilient o-rings, seals, ~askets, tubing and the like.

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~ Curing Characteristics i at 177C/24', ASTM D-2084 S
i M~ - ~IL, N-m 3.9 3.8 3.9 ts 0.2, min. 1.4 2.9 1~4 t' 50, min. 214 503 2.4 Mooney Scorch, 121C
Minimum 81 80 81 ¦ Minutes to 5-point rise 9.5 ~30 9.5 ¦ Test Results ¦!;; 15 Cured Samples Modulus - 100%, MPa 10.0 7.7 9.5 Tensile strength, MPa16.4 16.6 16.6 Elongation at Break, %160 185 155 Compression set, %
Pellets, 70h/204C42 39 41 Cured/Heat-Aged Samples:
Modulus - 100%, MPa 4.7 3.7 4.6 ¦ Modulus - 200%, MPa 7.6 6~8 7.5 ~; Tensile strength, MPa 8.3 8.8 8.3 Elongation at Break, ~260 300 265 _XAIIPLE 2 For purposes of comparison, a ~luoroelastomer composition outside the present invention is prepared, cured, and tested in the manner described in Example 1 except that the Hercules~ PE-200 used in Example 1 is o~itted from the composition.
Test results are shown in Table 1, where it can be seen that 5~3 minutes are required to reach 50% of full cure, compared with 2.4 minutes in Example l; and that the onset of cure (tS 0.2) is 5~
1~
2.9 minutes, compared with 1.4 mi~utes in Example 1.
Thus a very worthwhile improvement in curing rate is obtained in Example l~

Another fluoroelastomer composition of this invention is prepared, cured and tested in the manner described in Example l except that the 2.0 parts Hercules~ P~-200 u~ed in Example l has been replaced with 2.0 parts pure pentaerythritol.
Test results are shown in Table l, where it can be seen that the composition has a surprisingly fast cure rate and that the cured samples have very good physical properties, !~ 15 ~ Ano~her fluoroelastomer composition of this invention is prepared and cure-tested in the manner described in Example 1 except that the fluoroelastomer is a vinylidene fluoride/
hexafluoropropylene 60:40 dipolymer whose Mooney Viscosity (P~-10 at lOQC) is 60 and that the levels o~ benzyltriphenylphosphonium chloride, calcium hydroxi~e, magnesiu~ oxide, and pent~erythritol are reduced to 0.55, 2.0, 2.0, and l.0 parts, respectively, from the levels used in Example 3.
Test results are shown in Table 2, where i~
can be seen that the composition has a surprisingly fast cure rate and the cured samples have v~ry good physical properties, especially with respect to resistance to swelling by 100C water.

For purposes of comparison, a fluoroelastomer composition outside the present invention is prepared, cured, and tested in the manner described in Example 4, except that the pentaerythritol used in Example 4 is omitted~

Test resultQ shown in Table 2, where it can ¦ be seen that 10.3 mi~utes are required to reach 50~
! of the full state of cure, compared with 4.4 minutes 1 in Example 4, and that the resistance to swelling by ¦ 5 100C water is somewhat lower than that of the cured composition of Example 4- Thus, a very worthwhile improvement is cure rate and a somewhat better 1 resistance to swelling by 100C water is obtalned in ! Example 4.

!

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TABL~ 2 Examples Curing Characteristics at 177C/24', ASTM D-2084 MH , N-m 6.6 S.96.4 6.7 2.1 ML , N-m 0.5 0.50.6 0.5 0.4 tS 0.2, min. 3.2 6.93.8 4.4 11.8 10 t' 50 , min. 4.4 10.35.0 6.0 >24 Mo ~
__ Minimum 38 29 37 34 28 Points rise in 30 min. 0 <1 0 0 0 T~st Results .
Cured 5amples:
Modulus - 100%, MPa6.8 4.55.9 5.9 2.0 Tensile strength, MPa 10.510.8 12.2 9.9 7,3 Elongation at Break, ~ 170280 22~ 170 850 Compression set, %22 21 21 30 Pellets, 70h/204C
Water swell, volume ~ 2.32.9 5.1 1.5

7 d/100C

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EXA~P~E 6 For purposes of comparison, a fluoroelastomer composition outsid~ the present invention i5 prepared, cured, and tested in the manner described in Example 4, except that the levels of calcium hydroxide and magnesium oxide used in Example 4 are increased to 6.0 and 3.0, respectively, and that the pentaerythritol used in Example 4 is omitted.
Test resul~s are shown in Table 2, where it can be seen tha~ the composition has a cure rate that is somewhat slower than that of the composition of Example 4 and that the cured samples have very good physical properties, except for resistance to ; 15 swelling by 100C water. Thus, a very worthwhile improvement in resistance to swelling by 100C water is obtained with the cured composition of Example 4 at a cure ~ate that is hi~her than that of the uncured composition of Example 6.
EX~PLE 7 ~nother fluoroelastomer composition of this invention is prepared and cure-tested in the manner described in Example 4, except that the calcium hydxoxide level used in Example 4 is reduced to l.0 parts.
Test results are shown in Table 2, where it can be seen that the composition has a surprisingly fast cure rate and that the cured samples have very good physical properties, especially with respect to resistance to swelling by lOO~C water.

For purposes of comparison, a fluoroelastomer composition outside the present invention is prepared and subjected to the curing conditions as described in Example 7, except that the pentaerythritol used in Example 7 is omitted.
I

! 17 :. , ~ ~LZ~S~8 . Results are shown in Table ~, where it can ¦ be seen that the composition of Example 8 ~ails to reach a reasonably high cure state in 15 minutes at curing temperature, compared with the composition of Example 7, which reaches a high cure state in less than 15 minutes, and whose cured composition has excellent resistance to swelling by 100C water.
EX~MPLE 9 Another fluoroelastomer composition of this 10 invention is prepared and cure-tested in the manner described in Example 6, except that 1.87 parts dipentaerythritol, which is the monoether that results from mono-dehydration of two equivalents of pentaerythri~ol, is also present in the composition.
Curing characteristics and Mooney Scorch results are shown in Table 3, where it can be seen that the composition has a surprisingly high cure ~ rate compared to the cure rate of the composition of Example 6.

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; 35 . 18 !

5~E~
., TA~LE 3 _, Examples Curing Characteristics at 177C/24', ASTM D-2084 ~ t~ 0.2 , mi~. 2.5 2.2 J t' 50 , min. 3.3 3,1 Mooney_Scorch,_121C/30' Minimum 33 32 Minutes to 5-point rise ~30 23 .1 .
~ 15 i' . 35 EXA~PLE lO
Another fluoroelastomer composition of this invention is prepared and cure-tested in the manner descrlbed in Example 9, except that the 1.87 parts o~
dipentaerythritol used in Example 9 are replaced with ¦ 0.76 parts 2,2-dimethyl-1,3~propanediol~
Curing characteristics and Mooney Scorch results are shown in Table 3, where it can be seen that the composition has a surprisingly high cure rate compared to the cure rate of the composition of Example 6.
~XAMP1E ll I - Another fluoroelastomer composition of this invention is prepared and cure-tested in the manner described in Example 3 except that a) the 0.~0 parts ! benzyltriphenylphosphonium chloride of Example 3 is replaced by 0.98 parts of the mono-benzyltriphenylphosphonium salt of Bisphenol AF, l b) the 2-0 parts of Bisphenol AF is reduced to 1.53 1 2Q parts, c) the 2.0 parts of pentaerythritol of Example 1 3 is reduced to l.0 parts, and d) l~0 parts of pwchlorophenylsulfone are added.
Test results are ~hown in Table 4, where it is seen that the composition has a surprisingly fa~t cure rate and that the cured samples have very good physical properties in general and outstanding compre~sion set resistance and .scorch safety in particular.
EX~PL~ 12 For purposes of comparison, a fluoroelastomer composition outside the present invention is prepared and cure tested in the manner described in Example ll, except that the pentaerythritol used in Example ll is omitted.

~LZi~5~3 Resultc are shown in Table 4, where it can be seen that the composition of Example 12 has a much slower cure rate than thaf of the composltion of Example ll. Thus, a very worthwhile improvement in cure rate is obtained with the composition o~ Example ll co~pared with the c ompos i t i on of Example 12.

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T1~BI~E 4 Examples Curing Characteristics at ~
MH, N-m 6.3 6.0 ML, N~m 1.3 1.0 t$ 0.2, min. 2.4 6.9 t' 50, min. 4.0 11.7 1~ M~y ~ c/30~
Minimum 73 60 Points rise in 30 minutes 4 3 Test Results ~ :
Modulus - 100~, MPa 7.4 6.9 Tensile strength, MPa17.5 16.9 Elongation at Break, % 200 200 Com~ression set, % 38 40 Pellets, 7Oh/204C
Heat-Aqed Samples:
Modulus - 100%, MPa 3.1 ~.8 Modulus - 200%, MPa 5.3 5.3 Tensile s~rength, MPa6.9 7.7 Elongation at Break, % 315 330 12~0$9tB

E MPLE 13_ Another fluoroelastomer ~omposition o~ this invention is prepared and cure-tested in the manner aescribed in Example l,except that a) the terpolymer fluoroelastomer used in Example 1 is replaced b~ a te~rapolymer of vinylidene fluoride/
hexafluoropropylene/tetrafluoroethylene/3,3,4,4-tetrafluoro-4-bromobutene 35:34:29:2, whose Mooney Viscosity (ML-10 121C) is 60, b) the level of benzyltriphenylphosphonium chloride used in Example 1 is increased from 0.9 parts to 1.2 parts, c) the level of Bisphenol AF used in Example 1 is increased from 200 parts to 3.0 parts, and d) the level of Hercules~ PE-200 used in Example 1 is reduced from 2.0 p~rts to 0.5 parts.
Curing characteristics and Mooney Scorch resul~s are shown in Table 5, where it can be seen that the composition has a surprisingly high cure rate compared to the composition of Example 14. The increased cure rate of the composition o Example 13 compared to the cure rate of the composition of Example 14 is a significant advantage in keeping the molding cycle as short as possible.

~3 ~ ' _ 13 ~415 16 Curing Characteristics at 177C/~4', ASTM D-2084 MH , ~-m 6.7 6.7 5.9 5.8 ML , N-m 1.5 1.5 1.3 1.4 tS 0.2 , min. 2.3 3.2 2.7 3.1 t' 50 , min~ 4.0 5.6 5.5 7.0 Moo~e~ Scorch, 121C/30' Minimum 85 8064 67 Minutes to 5-point rise >15>15 19 19 Test Results ;~ Cured Sample~o ! Modulus 100%, MPa 9.9 9.2 5.2 4.8 Modulus - 200~, MPa - -12.011.7 Tensile strength, MPa 15.8 15.7 17.3 16~4 Elongation at Break, % 165170 290 290 Compression set, ~ 39 3784 81 Pellets, 70h/204C

1.

3 ~

E AMP~E l For purposes of comparison, a fluoroela~omer compo~ition outside the presen~
inv~ntion is prepared and cure tested in the manner described in Example 13, except that the Hercule PE-200 used in Example 13 is omitted.
Results are shown in Table 4, where it can be saen that the composition of Example 13 reaches 50~ of its full cure state in only 4.0 minutes and the co~position of Example 14 requires 5.6 minute~ to reach 50% of its full cure state.

Another fluoroelastomer composition of this invention is prepared and cure-tested in ~he manner described in Example 1, excep~ that a) ~he benzyltriphenylphosphonium chloride, Bi~phenol AF, and calcium hydroxide used in Example 1 are replaced by 3.0 parts N,N'-dicinnamylidene-1,6~hexanediamine, which is also known as DIAK #3* b) the level of magnesium oxide used in Example 1 is increased from 3 paxts to 15 parts, and c) the level of Hercules~
PE-200 used in Example 1 is reduced from 2.0 parts to 1.0 parts.
Curing charact er i st i cs and Mooney Scorch results are shown in Table 5, where it can be seen that the composition has a surpri singly high cure rate compared t~ the cure rate of the composition o~
Example 16. The increased cure rate of the composition of Example 15 compared to the cure rate of the composition of Example 16 is a significant advantage.
EX.~PLE 16 For purposes of comparison, a fluoroelastomer composition outside the prese~t invention is prepared and cure-tested in the manner *denotes trade mark described in Example 15, except that the Hercules~
PE-200 usefl in Example 15 is omitted.
Re~ults are shown in Table 5, where it can be sesn that the composition of Exampl~ 15 reaches 50% ~f its full cure state in only 5.5 minutes and the com~osition of Example 16 requires 7~0 minutes to reach 50% of its full cure state.

Claims

CLAIMS:

1. A curable composition comprising (A) a copolymer containing polyemerized vinylidene fluoride units, and polymerized hexafluoropropylene units, or polymerized chlorotrifluoroethylene units, or polymerized 1-hydropentafluoropropylene units or polymerized 2-hydropentafluoropropylene units, (B) a quaternary phosphonium or quaternary ammonium vulcanization accelerator, (C) a crosslinking agent selected from the group consisting of dihydroxy-, trihydroxy- and tetrahydroxy- -benzenes, -naphthalenes and -anthracenes having an aromatic ring, and bisphenols of the formula wherein A is a difunctional radical, x is 0 or 1 and n is 1 or 2, (D) a polyol coaccelerator selected from the class consisting of pentaerythritol, 2,2-dimethyl-1,3-propanediol, dipentaerythritol, and trimethylol propane.
(E) a metal compound selected from the group consistin of divalent metal oxide, divalent metal hydroxide and mixtures of such oxides and hydroxides with metal salts of weak acids.
said composition containing for each 100 parts by weight of component A, about 0.2 to 2 parts by weight of component (B), about 0.5 to 4 parts of component (C), about 0.05 to 4 parts of component (D), and 0.5 to 30 parts of component (E).

2. The composition of claim 1 in which the polyol is pentaerythritol.

3. The composition of claim 1 in which the polyol is 2,2-dimethyl-1,3-propanediol.

4. The composition of claim 1 in which the polyol is dipentaerythritol.

5. The composition of claim 2 in which the divalent metal oxide is calcium oxide.

6. The process of forming a fluoroelastomer which comprises heating the composition of claim 1 in a containing zone.